def get_users_info(openid_list):
    count = 3
    start = 0
    end = count
    openid_list_len = len(openid_list)
    while start < openid_list_len:
        open_id_str = '_'.join(openid_list[start:end])
        print open_id_str
        start += count
        end   += count


openid_list = ['1', '2', '3', '4', '5', '6', '7', '8']
get_users_info(openid_list)

